Towards a high-accuracy Ba4+ quantum-logic clock
Abstract
The 338.8 THz (884.9 nm) electric quadrupole transition between the ground and first-excited electronic states in quadruply-ionized,barium (BaV) is a promising candidate for a high-accuracy optical atomic clock. The lifetime of the excited clock state is 8.3 s, wh,ich allows for low statistical uncertainty, even with a single ion, for practical averaging times. The differential static scalar po,larizability is small and negative, providing suppressed sensitivity to blackbody radiation and allowing cancellation of excess micr,omotion and Stark shifts. The charge-to-mass ratio of BaV is well-suited to sympathetic cooling and quantum-logic readout using a co,-trapped calcium ion. Considering all known systematic shifts, the total fractional systematic uncertainty for this clock has been e,stimated to be one part in ten to the nineteen, or below. To this end, I propose to develop a quantum-logic clock based on BaV.Over,the past two decades, significant progress has been made in the developmentof atomic clocks based on optical transitions. State-of-t,he-art optical atomic clocks interrogate either an ensemble of neutral atoms confined in an optical lattice, or an individual ion co,nfined in a Paul trap. Ion clocks demonstrated thus far employ singly charged ions, however, several laser-accessible transitions in, highly charged ions (HCIs) have been identified which possess both a high quality factor and insensitivity to environmental perturb,ations, making them potential candidates for new optical atomic clocks. Recent theoretical work suggests that optical clocks based o,n fine structure transitions in HCIs that could realize fractional systematic uncertainties below one part in ten to the twenty. How,ever, the relatively short excited state lifetimes of these systems present a major challenge in developing a clock that will posses,s both low systematic uncertainty (accuracy) and low statistical uncertainty (frequency instability). To address these and other lim,itations in previous proposals, I present BaV as an exciting new direction for the development of a high-accuracy quantum-logic cloc,k.BaV has several features which make it an attractive candidate for a new quantum-logic clock. These include, (i) a clock transitio,n with a low sensitivity to blackbody radiation, (ii) a charge-to-mass ratio which is well matched to sympathetic cooling and quantu,m-logic operations using a co-trapped calcium ion, and (iii) a clock transition wavelength of 884.9 nm which is easily addressed usi,ng commercial solid-state lasers. In addition, the clock transition possesses a negative differential scalar polarizability which le,ads to an experimentally convenient magic rf drive frequency of approximately 100 MHz. When operated at this frequency, the microm,otion-induced time-dilation shift is cancelled by the correlated scalar Stark shift. This feature in BaV effectively removes one of,the major sources of systematic uncertainty which currently limits other optical atomic clocks.For the project proposed here, I plan, to develop the first quantum-logic clock based on a highly charged ion. The future naval relevance of this work is related to preci,se timekeeping requirements which are needed for future improvements to naval navigation. The work proposed here aims to address sev,eral performance (accuracy and instability) limitations that exist in previously demonstrated optical clocks. This new clock could l,ead to the development of an improved time and frequency standard for use in various naval applications.Approved for Public Release.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- N000142212070
Entities
People
- Samuel Brewer
Organizations
- Colorado State University
- Office of Naval Research
- United States Navy